The use of void-containing microcapsules as opacifying agents in coatings is known in the art, e.g., see U.S. Pat. Nos. 3,585,149, 3,669,899, 3,707,514 and 3,779,941. As pointed out in U.S. Pat. No. 3,779,941, these void-containing microcapsules possess an opacifying power which is equal to or substantially greater then inorganic pigments (e.g., titanium dioxide) on a weight basis. However, while these void-containing microcapsules provide excellent opacity to films formed from coating compositions in which they are incorporated, techniques heretofore employed in producing such coating compositions (e.g., paints) have proven to be costly and time-consuming. Thus, in prior processes, as exemplified by the above-mentioned patents, the void-containing microcapsules are first produced by one of several processes and then incorporated into the coating composition by admixture thereto followed by stirring. As will be apparent, such processes involve a number of processing steps and procedures and require careful handling of the microcapsules. Typical of processes which illustrate such prior processes is that of U.S. Pat. No. 3,779,941. As disclosed in that patent, air-containing microcapsules (i.e., microcapsular opacifiers) are prepared by admixing a solution comprising an oil-soluble, partially condensed thermosetting condensation product in a water-immiscible, oily material and an aqueous solution of a water-soluble polymeric material, thereby forming an emulsion, following which the emulsion is treated in such a manner as to form microcapsules containing the oily material, thereby producing precursor microcapsules and, finally, the precursor microcapsules are treated (i.e., heated) to expel the oily material and replace it with air. As disclosed in this patent, these microcapsules, either in the form of air-containing microcapsules or precursor microcapsules (i.e., containing oil) are then dispensed in the paint composition. As will be evident, this requires a considerable number of processing steps to form the microcapsules and then it is necessary to employ an additional step in incorporating the microcapsules into the paint composition. As indicated previously, this is an expensive and time-consuming process.
Accordingly, it would be highly advantageous in terms of cost and processing time if the microcapsules could be produced in-situ during the manufacturing process of the coating composition, or in a film formed from the coating composition. The present invention accomplishes this desirable result while providing for the advantages of opacity and gloss control while such microcapsules impart to films formed from such coatings.